Premium
Design of Metabolic Engineering Strategies for Maximizing l ‐(–)‐Carnitine Production by Escherichia coli . Integration of the Metabolic and Bioreactor Levels
Author(s) -
Sevilla A.,
Vera J.,
Díaz Z.,
Cánovas M.,
Torres N. V.,
Iborra J. L.
Publication year - 2008
Publication title -
biotechnology progress
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.572
H-Index - 129
eISSN - 1520-6033
pISSN - 8756-7938
DOI - 10.1021/bp0497583
Subject(s) - bioreactor , metabolic engineering , biochemical engineering , biological system , escherichia coli , carnitine , dilution , process engineering , chemistry , chemical engineering , biochemistry , biology , enzyme , thermodynamics , physics , engineering , organic chemistry , gene
In this work metabolic engineering strategies for maximizing l ‐(–)‐carnitine production by Escherichia coli based on the Biochemical System Theory (1 – 3) and the Indirect Optimization Method are presented (4). The model integrates the metabolic and the bioreactor levels using power‐law formalism. Based on the S‐system model, the Indirect Optimization Method was applied, leading to profiles of parameter values that are compatible with both the physiology of the cells and the bioreactor system operating conditions. This guarantees their viability and fitness and yields higher rates of l ‐(–)‐carnitine production. Experimental results using a high cell density reactor were compared with optimized predictions from the Indirect Optimization Method. When two parameters (the dilution rate and the initial crotonobetaine concentration) were directly changed in the real experimental system to the prescribed optimum values, the system showed better performance in l ‐(–)‐carnitine production (74% increase in production rate), in close agreement with the modelapos;s predictions. The model shows control points at macroscopic (reactor operation) and microscopic (molecular) levels where conversion and productivity can be increased. In accordance with the optimized solution, the next logical step to improve the l ‐(–)‐carnitine production rate will involve metabolic engineering of the E. coli strain by overexpressing the carnitine transferase, CaiB, activity and the protein carrier, CaiT, responsible for substrate and product transport in and out of the cell. By this means it is predicted production may be enhanced by up to three times the original value.